Spring contact high voltage connector



1958 P. w. KASEMAN 2,847,595

SPRING CONTACT HIGH VOLTAGE CONNECTOR Filed Jan. 6, 1956 INVENTOR. PHu W KHSEMHN nited States Patent Psi SPRINGCONTACT HIGH VOLTAGE CONNECTOR Paul W. Kasernan, Lancaster, Pa., assignor to Radio Corporation of America, a corporation of Delaware Application January 6, 1956, Serial No. 557,695

9 Claims. (Cl. 313-64) This invention relates to electric discharge devices, and more particularly it relates to lead-in means for such devices.

A principal object of the invention is to provide an improved voltage supply cable and terminal contact thereon, for applying relatively high voltages to an electrode of electric discharge tubes and the like.

Another object is to provide a high voltage leadin and contact arrangement for such devices as cathode ray tubes and the like, having a cable and contact unit ermanently sealed into the wall of the tube.

A further object is to provide an improved spring, contact arrangement for making electric contact between a high voltage supply cable and a contact button.

A feature of the invention relates to an improved high voltage supply cable and spring contact unit for making contact with a contact button sealed into the glass wall of an enclosing bulb, whereby the likelihood of undesirable corona discharge is avoided between the cable conductor and adjacent surfaces which are at ground or other relatively low potential.

Another feature relates to a novel voltage supply connector for a high voltage electrode of such devices as cathode ray tubes and the like, which connector is machanically strong, of small size or bulk, and is substantially free from undesirable corona discharges.

Another feature relates to a high voltage lead-in cable having an insulated center conductor for supplying a high voltage to a contact member, such for example as a sealed-in contact button, the said center conductor being surrounded by a coil flexible Wire which provides a resilient pressure contact with said button, while at the same time acting as a corona shield around the exposed end of said center conductor.

A further feature relates to a high voltage lead-in insulated cable for making contact with a contact member such as a sealed-in contact button of the cavity kind, and a coiled spring wire having a portion coiled around the cable insulation and a plural-turn portion surrounding the exposed end of the cable conductor and arranged to be held in spring-pressed engagement with the bottom of said button cavity, and with the tip of the cable conductor permanently joined to one of said plural turns, and leaving a number of said plurality of turns to be compressed against the bottom of said cavity.

A further feature relates to a high voltage supply cable for permanent attachment to the wall of an electron tube such as a cathode ray tube, the said cable comprising a center conductor carrying an insulation sheath, and a terminal contact for said center conductor in the form of a coiled spring wire having a plurality of turns coiled around and gripping said sheath, and having another plurality of turns extending beyond the end of said sheath for making resilient pressure contact with a stationary contact member of the cavity kind which is carried by the wall of the tube, the center conductor being exposed at its end and fastened to an intermediate one Of said other plurality of turns; in conjunction with a 6 a! tubular solid insulator body molded around the end of said sheath and around the first plurality of turns of said coiled spring and also in molded contact against the wall of the tube surrounding said button to completely seal the cavity therein.

A further feature relates to a high voltage supply cable and integral molded terminal contact assembly for such devices as cathode ray tubes of the image projection kind which employ a high voltage electrode, and wherein the contact assembly is of small bulk but is nervertheless mechanically strong and free from disturbing corona effects.

A still further features relates to the novel organization, arrangement and relative location and interconnection of parts which cooperate to provide an improved high voltage cable lead-in and contact arrangement for high voltage electron tubes and the like.

While the invention finds its immediate utility in connection with high voltage cathode ray tubes, and therefore is illustrated as embodied in such a tube, it will be understood that it is capable of use in any high voltage device wherein positive electrical contact is required between a high voltage supply conductor and a terminal of the device, and wherein a minimum of bulk in the contact arrangement, are desiderata. Accordingly, in the drawing,

Fig. l is a schematic elevational view of a cathode ray tube and high voltage lead-in cable arrangement embodying the invention.

Fig. 2 is a detail view of part of the high voltage supply cable and terminal contact therefor.

Fig. 3 is an enlarged sectional view of part of Fig. 1 taken along the line 3--3 thereof and viewed in the direction of the arrows.

Fig. 4 is a modification of the invention.

Various forms of cable connections have been used heretofore to make contact between the end of a cable wire and a contact button sealed through the glass wall of an enclosing bulb. One such arrangement comprises some kind of snap-fastener combination, employing a rounded ball-like member fastened to the end of the cable wire, which member is then inserted into a cooperating cavity button sealed in the glass Wall of the bulb. Another known arrangement employs some kind of flexible member carried by the cable wire and arranged to be forced or clipped into the contact button cavity. While such known arrangements are useful in connection with ordinary electron tubes they do not necessarily meet all the stringent requirements of certain kinds of cathode ray tubes which are to be operated at very high anode voltage. For example, in well known forms of projection type cathode ray tubes, voltages of 20,000 or higher, may be necessary, and in certain applications of such tubes it is important that the external connection unit to the high voltage electrode be of small bulk so as not to reduce the efliciency of the optical projection or reflection system that is used with the tube. Furthermore, it is very important that the end of the high voltage supply cable be protected against corona discharge to surrounding objects. It is highly important that the connection between the cable terminal and the contact button on the tube, be mechanically strong, and the interior of the button cavity be protected from contamination or corrosion. The present invention provides a solution which meets all the above-noted requirements.

Referring to the drawing, the numeral It indicates any known kind of cathode ray tube having an evacuated enclosing envelope comprising, for example, the neck 11, bulb 12 and face plate 13, the neck being closed by any suitable header through which the various lead-in wires to certain electrodes are sealed in a vacuum-tight manner. Suitably mounted within the neck 11 is any well known form of electron gun (not shown) for developing a beam of electrons. The face plate 13 has on its inner surface a coating or screen 14 of phosphor material which fluoresces upon impact by the electron beam. It will be understood that the beam is moved in a pointby-point scanning pattern over the screen 14 under the control of any well known beam deflecting means (not shown).

In order to produce the requisite intensity of fluorescent light from the screen 14, it is necessary to employ a second or final anode which must be connected to a source of high direct current potential, for example of as much as 20,000 volts or higher. This second or final anode usually includes a conductive coating 15 of graphite or the like, on the internal surface of neck 11 and on the internal surface of the bulb 12, and extending to a point just short of the screen 14. For the purpose of reducing current leakage along the external surface of the bulb around the high voltage anode connection, the bulb may be provided with an external coating 16 of any well known insulation.

In order to make electric contact with the high voltage or final anode coating 15, there is sealed into the wall of bulb 12, a hollow metal button 17 having, for example, a flat bottom 18 with a tapered side wall 19. Preferably wall 19 is sealed into the glass wall of the bulb so that its lip is substantially flush with the outer surface of the bulb and with the button projecting inwardly below the inner surface of the bulb wall. It will be understood that the invention is not limited to the particular shape of contact button shown in the drawing, provided it is of a kind which has a cavity to receive the cable terminal to be described. After the button has been sealed into the bulb wall, the inner surface of that wall is provided in any Well known manner with a conductive coating 15 which constitutes part of the final anode of the tube, and which coating covers the inwardly projecting surface of the button 17, as shown in Fig. 3.

For the purpose of applying the requisite high voltage to the coating 15, there is provided according to the invention, a high voltage cable 21 having a center conductor 22 with an insulation sheath or covering 23 of high dielectric strength. A portion of the sheath 23 is removed to expose the center conductor 22, whose tip is bent and soldered or welded to one of the turns of a coiled spring wire 24. The wire 24 is tightly coiled around the insulation sheath 23 so as to grip it firmly, and leaving a plurality of turns, for example five turns, as seen in Figs. 2 and 3, extending beyond the end of sheath 23. The invention, of course, is not limited to any specific number of turns in the coiled spring 24. Thus the number of turns which surround the sheath 23 may be just sufficient to provide the necessary firmness of spring grip thereon. Preferably, however, the turns which extend beyond the sheath 23 are of gradually increasing diameter. In the particular embodiment shown, the lowermost four turns of the coiled spring have an overall axial length d which is substantially greater than the depth of the button. Consequently when the cable with its coiled spring terminal is pressed into the button cavity, the said four turns are somewhat resiliently compacted in nested relation and the lowermost turns seat against the bottom and side walls of the button, thus insuring a relatively large area and positive spring-pressed contact.

Since the end of the center conductor of the cable is offset and fastened to one of the spring turns, for example the third turn from the end, as shown in Figs. 2 and 3, the said turns surround the exposed end of the conductor, and because of the very much larger diameter of the turns as compared with the diameter of the conductor, they act as a corona shield for the center conductor. Furthermore by fastening the tip of the center conductor to an intermediate turn of the coiled spring,

a substantial degree of lateral flexibility is provided without danger of breaking the contact. If the center conductor of the cable were soldered or welded directly to the button or to a solid member such as a knob to be inserted into the button with a relatively close and tight fit, bending of the cable adjacent the bulb might result in breaking the cable conductor or its connection to the button.

If desired, the button 17 may be provided with an annular lip 25 (Fig. 4) so that when the coiled spring terminal is pressed into the button and the end turns are thereby compressed, they can then spring back to engage the under face of the annular lip so as to make contact therewith and also to lock the coiled terminal within the button.

Preferably however, after the cable has been connected to the button by compressing the end turns within the button, the assembly has molded therearound a tubular collar 26 of a moldable electric insulating resin, such as an epoxy resin, which upon hardening forms a rigid unit with the end of the cable. During this molding operation an annular flange 27 is also formed on collar 26, which flange is bonded to the external surface of the glass bulb. This serves to rigidize the contact assembly and to unite it as a permanent attachment to the bulb. The molded collar 26 also seals the cavity within the button 17 thus protecting the contact area between the coiled spring terminal and the button against corrosion and accumulation of dust.

It should be observed that the coiled spring which surrounds the exposed end of the cable conductor, provides a conductive surface which is of much greater diameter than the diameter of the cable conductor, and therefore, it reduces the likelihood of corona discharge to adjacent objects, since the dielectric stresses are distributed over a much larger area which is free from sharp or pointed projections.

Various changes and modifications can be made in the shape, size and composition of the various elements constituting the invention without exceeding the scope thereof.

What is claimed is:

1. A lead-in for electric devices such for example as electron tubes, comprising a supply conductor, having an exposed end portion, a coiled multi-turn wire spring surrounding said exposed end portion and having a plurality of turns extending beyond the exposed end of said conductor, the tip of said conductor being electrically fastened to an intermediate one of said plurality of turns.

2. A lead-in for electric devices such for example as electron tubes, comprising a supply conductor having an insulation sheath with one end of the conductor exposed beyond the end of the sheath, a multi-turn coiled spring wire. surrounding said exposed end and having at least one turn coiled around said sheath, and an additional pluralityof turns extending beyond the exposed end of said conductor, said conductor having its tip electrically joined to an intermediate one of said plurality of turns.

3. A lead-in according to claim 2 in which said plurality of turns are of progressively increasing diameter.

4. A lead-in according to claim 2 in which said supply conductor is substantially concentric with said turns and has its tip bent at an angle and fastened to said intermediate turn.

5. A high voltage lead-in for electric devices of the kind having a cavity contact member to be electrically connected to said lead-in, said lead-in comprising a supply conductor having an insulation sheath, said conductor having one end exposed beyond the sheath, a multi-turn spring wire surrounding said exposed end and having at least one turn coiled around the sheath and gripping said sheath, an additional plurality of turns extending beyond the exposed end of said conductor, said conductor having its tip fastened to one of said plurality of turns,

5 and an insulation collar molded around said sheath and certain of said turns and also having an integral molded flange to seal the cavity in said contact member while permitting the end turns of said plurality of turns to be held in spring-pressed contact with the interior surface of said cavity.

6. A cathode ray tube comprising an envelope, a high voltage anode coating on the internal surface of a wall of said envelope, a cavity contact button sealed through said wall and in contact with said coating and with the cavity facing outwardly of said Wall, a high voltage lead-in comprising a cable having a conductor with an insulation sheath and with the end of the conductor exposed beyond the end of the sheath, a coiled spring wire encircling said exposed end and having at least one turn gripping said sheath and an additional plurality of turns extending beyond the exposed end of said conductor, the tip of said conductor being united to an intermediate turn of said plurality of turns, and means to retain said plurality of turns in compacted spring-pressed contact with 20 the inner face of said cavity.

7. A cathode ray tube according to claim 6 in which the last-mentioned means includes a tubular insulator body molded around the end of said cable and also molded to the exterior surface of said wall around said button.

8. A cathode ray tube according to claim 6 in which the last-mentioned means includes a lip on said button which latches with at least one turn of said plurality of turns when said turns are pressed into said cavity.

9. A cathode ray tube according to claim 6 in which the turns of said plurality of turns are of progressively increasing diameter to permit the turns to be compacted in nested resilient array when pressed into contact with the inner surface of said cavity.

References Cited in the file of this patent UNITED STATES PATENTS 

